People cash out because they need the money or think that leaving their money in their wallet will result in them losing it. They don't power up because it takes a month to power down. Let's face it, most people are drawn to platforms like Steemit to make some easy money, when they find out it is not really that easy they give up, but of course cash out whatever they were able to accumulate.

Motivating people to power up is a really difficult task, like I pointed out most people sign up for some easy money and staying on the platform for a long time is not something they have even considered. It is hard to motivate, higher votes will probably mean quicker cash outs.

You can't make SP more appealing, it is what it is, the platform depends on those already here who hold big amounts of Steem or those who join and are willing to invest in Steem.

The eco-system has sustained itself via the big investors and will continue to do so, unless, for some reason these big holders decide their time on Steemit is up. If that happens it means good bye to the platform.

I know this because I have usually cashed out when I get to a certain amount. Right now, what I hold, is the most Steem I have ever had.